The Ospreys 22 Ulster 21: Ulster saw a crucial victory over Celtic League leaders Neath-Swansea Ospreys snatched from their grasp in controversial style by a penalty from Wales star Gavin Henson at St Helen's.
A third penalty from the boot of David Humphreys, after Tommy Bowe and Andrew Maxwell had both scored tries, looked to have secured a precious away win over the table-toppers.
But a minute into injury-time, Scottish referee Rob Dickson made a borderline call by judging replacement Rowan Frost offside in front of the posts, having given the Ospreys field position with a similarly controversial knock-on decision against Kieran Campbell, to allow Henson his chance.
It was a cruel blow for Ulster who were hit by the late withdrawal of Tyrone Howe with a groin injury but were relieved to at least have Humphreys following fears that he had fractured a cheekbone against Cardiff.
Henson moved to full back for the Ospreys and it took less than three minutes for him to make an impact.
Humphreys hoisted a lazy up-and-under in midfield and Henson easily beat Paul Steinmetz to the ball and strode effortlessly through from the half-way line to score the opening try.
Having missed his first attempt at goal into the wind, Humphreys calmly slotted the second from distance before setting up Ulster's first try with a deft inside pass that split the Ospreys' rush defence, Maxwell profiting from Steinmetz's break and Roger Wilson's link.
Humphreys exchanged penalties with Henson but successive penalties either side of half-time stretched Ospreys' lead until a moment of magic from Campbell.
Ulster's scrumhalf broke from behind his forwards before showing great awareness to slide through an angled kick for the on-rushing Bowe to touch down.
OSPREYS: G Henson; S Terblanche, D Bishop, D Tiueti, S Williams; M Jones, J Spice; P James, B Williams (capt), A Jones, B Cockbain, J Thomas, A Lloyd, R Jones, S Tandy. Replacements: A Durston for M Jones (half-time), A Newman for Cockbain (54 mins); R Pugh for Tandy (65); E Seveaili'l for Tiueti (70); A Millward for A Jones (73).
ULSTER: B Cunningham; T Bowe, P Steinmetz, K Maggs, A Maxwell; D Humphreys, K Campbell; S Best, R Best, R Moore, G Longwell, M McCullough, C Feather (capt), R Wilson, N Best. Replacements: A Ward for Feather (70 mins); R Frost for Longwell (71).
Referee: R Dickson (Scotland).
